We investigated the effects of tillage practices on the densities of wolf spiders and planthoppers and leafhoppers in rice paddy fields. Paddies were subjected to one of two different treatments (no tillage and conventional tillage), and seasonal changes in the densities of wolf spiders and hoppers were investigated over two growing seasons (1999 and 2000). In both years, the density of wolf spiders was significantly higher and the density of hoppers tended to be lower in no-tilled paddies than in conventionally tilled paddies, although the latter difference was not statistically significant. The Iwao's omega values, which represent the degree of correlation between the spatial distributions of wolf spiders and hoppers, were higher in no-tilled than in tilled paddies during August when the hopper density decreased in notilled paddies.

To examine the effects of tillage practices on spider assemblages in rice paddy fields, we investigated the abundance and biomass of spiders in untilled and tilled paddy fields over three cropping seasons (from 1999 to 2001). In total, we collected 6,829 spiders, consisting of 13 species in seven families. The family Lycosidae was the most abundant, followed by Tetragnathidae, Linyphiidae, and Salticidae. Spider abundance and biomass were greater in untilled than in tilled paddies during each cropping season. Although we detected no significant effect of tillage on spider abundance, we did observe a significant effect of tillage on spider biomass in 2000 and 2001. No differences were found in the abundance and biomass of tetragnathid and linyphiid spiders during the cropping season. In contrast, the abundance and biomass of lycosid or salticid spiders tended to be larger in untilled paddies than in tilled paddies, especially later in the cropping season.

The diets of the wolf spiders Pardosa pseudoannulata and Pirata subpiraticus were elucidated by direct observation in paddies from July to September 2000. In July, dipterous insects were the most numerous prey consumed by P. pseudoannulata and the second numerous prey consumed by P. subpiraticus, comprising over 50% and over 20% of their respective diets. In contrast, in August, the proportion of dipterous insects decreased dramatically and hoppers were the most numerous prey, comprising over 60% and over 70% of all insects and spiders consumed by P. pseudoannulata and P. subpiraticus, respectively. In September, predators such as wolf spiders and aquatic Heteroptera were frequently observed in their diets. Overall, the green rice leafhopper, Nephotettix cincticeps, was the most numerous prey consumed by P. pseudoannulata and P. subpiraticus, followed by chironomids.

The smaller tea tortrix, Adoxophyes honmai (Lepidoptera: Tortricidae), is an economically important pest of tea in Japan. Previous work showed that a fast-killing nucleopolyhedrovirus (NPV) isolated from A. orana (AdorNPV) and a slow-killing NPV isolated from A. honmai (AdhoNPV) are both infectious to A. honmai larvae. Field application of these different NPVs was conducted against an A. honmai larval population in tea plants, and the control efficacy and transmission rate of the two NPVs were compared. The slow-killing AdhoNPV showed lower field efficacy, in terms of preventing damage caused by A. honmai larvae against the tea plants, than the fast-killing AdorNPV. However, AdhoNPV had a significantly higher horizontal transmission rate than AdorNPV. These results show that AdorNPV is suitable as an inundative agent, while AdhoNPV is an appropriate inoculative agent.